Vacuum switch for alternating current interruption

ABSTRACT

A vacuum switch for alternating current interruption comprises two pairs of separable operating contacts arranged in a vacuum chamber and connected in an alternating current circuit. A semiconductor diode is mounted within the vacuum chamber and connected for bridging one of the pairs of operating contacts. Drive means are provided for actuating said pairs of contacts in such manner that for interrupting the alternating current circuit the pair of contacts which is bridged by the semiconductor diode is caused to separate prior to separation of the other pair of contacts.

United States Patent Roth 1 Jan. 18, 1 972 VACUUM SWITCH FOR ALTERNATIN R f rences Cited CURRENT INTERRUPTION UNITED STATES PATENTS 1 Switzefland 2,896,125 7/1959 Morton ..200/144 AP [73] Assignee: Sprecher & Schuh A.G., Aarua, switz 3,038,980 6/1962 Lee ..200/144 B [and 3,174,019 3/1965 Jansson ..200/144 B 3,395,316 7/1968 Denes et al.. ..200/144 AP X [221 Flled= 16,197" 3,475,574 10/1969 Stolarz ..200/144 AP 21 A l.No.: 81 75 1 pp ,3 Primary Examiner-Robert S. Macon Related US. Application Data Attorney-Waters, Roditi, Schwartz & Nissen [63] Continuation-impart of Ser. No. 706,384, Feb. 19, A

1968, abandoned. [57] ABSTR CT A vacuum switch for alternating current interruption com- [30] Foreign Application Priority Data prises two pairs of separable operating contacts arranged in a vacuum chamber and connected in an alternating current cir- Feb- 21, Swltzel'land cu t. A semi nducto ode i moun e a m chamber and connected for bridging one of the pairs of 2% zoo/144B ZOO/144A? 317/11 operating contacts. Drive means are provided for actuating E said pairs of contacts in such manner that for interrupting the alternating current circuit the pair of contacts which is bridged by the semiconductor diode is caused to separate prior to separation of the other pair of contacts.

3 Claims, 2 Drawing Figures VACUUM SWITCH FOR ALTERNATING CURRENT INTERRUPTION This application is a continuation-in-part of my prior application Ser. No. 706,384 filed Feb. l9, 1968, and now abandoned.

This invention relates to a vacuum switch for alternating circuit interruption comprising two pairs of operating contacts arranged in a vacuum chamber and connected in an altemating current circuit for sequential opening by drive means.

A known vacuum switch comprises a vacuum chamber formed by a cylindrical envelope of insulating material and provided with two end caps forming a vacuumtight closure of the envelope. Two parallel contact rods extend through one of the envelope closure caps. The first contact rod is fixed to the closure cap, while the second contact rod is fixed in a vacuumtight connection to a bellows, so that this second contact rod can be moved inwardly and outwardly of the vacuum chamber. The other closure cap also carries a bellows in vacuumtight manner to which a third contact rod is fixed. The end of this third contact rod is fork-shaped and each fork-end forms an operating contact with the first and with the second contact rod. The end of the third contact rod projecting out of the vacuum chamber is connected with a drive, for example with electromagnetic drive means in order to move the contact rod into the vacuum chamber for closing the operating contacts or to pull it out of the chamber for opening the operating contacts. In order to obtain opening and closing of the operating contacts in timed succession, the second contact rod is arranged for limited longitudinal movement between two abutments and is urged by a spring against the inner one of the two abutments, so that when the third contact rod is moved in contact closing direction first the operating contact formed by the second contact rod is closed and afterwards the operating contact formed by the first contact rod, and when the third contact rod is pulled out of the vacuum chamber, the opening of the two operating contacts is effected in inversed succession. The two first contact rods are connected with one another by a resistor at the exterior of the vacuum chamber, so that the two operating contacts are placed in parallel and the flow of current through a single one of the contacts is limited in order to facilitate extinguishing of the are which is formed when the operating contacts are separated under load. In order to obtain very short break times and to extinguish the are already with a short contact travel, a high vacuum is required. However, a tight vacuum can be produced and maintained only when the vacuum switch is degassed at elevated temperatures. in order to enable a degassing operation at high temperatures, the resistor at the exterior of the vacuum chamber must be connected with the two contact rods subsequent to the degassing operation. For this it is necessary that the first or second contact rod is insulatedly arranged in the envelope closure caps. The known vacuum switch referred to above accordingly comprises a certain number of components to be assembled in vacuumtight connection; this results not only in a complicated and expensive, but also voluminous construction. The production of switching devices having fixed or movable electrically insulated lead-through conductors for high voltage is more difficult and time consuming than the production of noninsulated lead-through components and results in a considerable percentage of rejects during manufacture.

it is an object of the present invention to provide a vacuum switch having no electrically insulated lead-through conductors and which is easy and simple in manufacture and can be produced in smaller dimensions than the conventional vacuum switches.

The invention is based on the knowledge that it is possible, when using semiconductors diodes in alternating current interrupters, to prevent or limit the formation of the opening arc to only a commutation arc of short duration. Thus, for example, in power-switching arrangements for disconnection of al temating current circuits two contact break distances are connected in series and one of them is bridged by a diode. That break distance which is not bridged serves in this case as a voltage separator and is opened during the blocking period of the semiconductor diode for interruption of the alternating current circuit, such opening occurring immediately after the break distance bridged by the semiconductor diode has been opened, when the diode is current-carrying shortly before zero axis crossing of the alternating current. Precise timing of the break distances, however, is difficult and for this reason, frequently, arrangements are used having two series connected break-distances and a plurality of diodes and switch reactors.

The vacuum switch according to the present invention comprises two pairs of operating contacts arranged in a vacuum chamber and operable by drive means. A semiconductor diode is arranged in the vacuum chamber and one of the two pairs of operating contacts is bridged by the semiconductor diode, the operating contacts being actuated by said drive means so that for breaking the alternating current circuit the pair of operating contacts bridged by said semiconductor diode opens prior to opening of the other pair of operating contacts, and said drive means comprises control means which admit actuation of the contacts only'when the alternating voltage at the semiconductor diode is poled for forward direction.

As it is conventional with vacuum switches, the vacuum chamber can be formed by a cylindrical envelope of electrically insulating material provided with two end closure caps sealed with the cylindrical portion in vacuumtight connection, these caps carrying the contact carriers for the operating contacts. In contradistinction to conventional arrangements no electrically insulated lead-through conductors are required, since the semiconductor electrode is arranged within the vacuum chamber and may be mounted on one of the closure caps together with a fixed contact carrier, while the other closure cap serves for mounting a movable contact carrier which also does not require an electrically insulated lead-through. Due to the use of a semiconductor diode, the alternating current interruption practically occurs without formation of an arc, so that upon disconnection the operating contacts will not be subjected to particularly high temperatures and only minute quantities of contact material will evaporate, and the hardness of the vacuum will not essentially diminish even for long periods of operation. The internal surfaces of the vacuum chamber do not require to be extremely clean. Experience has shown that a degassing of the vacuum chamber at to 200* C. and possibly the introduction of a getter will suffice for a completely unobjectionable operation of the vacuum switch. Such baking out temperatures do not affect the semiconductor diode. For closing and opening the operating contacts any conventional drive can be used, for example an electromagnetic dn've. Care must be taken only that the operating contact which is bridged by the semiconductor diode can only then be opened when the diode is current-carrying, i.e., the alternating voltage connected thereto is poled for forward passing or gating. This can be obtained by known control means, for example by polarized relays or conventional electronic circuits, which admit a release of the electromagnetic drive only for example upon occurrence of positive half-waves of the alternating current.

Other objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings.

FIG. 1 shows diagrammatically and in axial section a vacuum switch according to the invention, having two series connected operating contacts and a simple drive means therefor.

FIG. 2 is a similar view of a vacuum switch according to the invention, having two operating contacts connected in parallel.

In both embodiments shown, the vacuum chamber, as mentioned, is formed by a cylindrical envelope 1 of electrically insulating-material, for example of glass or of a gastight sintered material. This envelope is sealed at both ends in vacuumtight connection by metallic closure caps 2 and 3 respectively. In

both embodiments. a first contact carrier rod 4 is fixedly inserted in the upper closure cap 2 and is in electrically conducting relation with the closure cap. Such a lead-through can be easily produced and sealed in vacuum-tight manner without any difficulties. The end of the contact carrier 4 situated within the vacuum chamber is formed as contact member for one of the operating contacts, and the opposite end projecting out of the chamber is destined for connection to one conductor 24 of the alternating current circuit to be interrupted. The casing of a semiconductor diode 11 is mounted on the inner side of the closure cap 2, one of the terminals of the semiconductor diode, for example the anode is electrically connected by the metal cap 2 with the first contact carrier 4.

The metallic bottom closure cap 3 supports a bellows 12 of spring metal, also arranged within the vacuum chamber for protection against being damaged. The edge of the open end of the bellows is in electrical and vacuumtight connection with the closure cap 3. The closed end of the bellows is fixed to a second contact carrier 5. The connection between the contact carrier 5 and the bellows 12 is vacuumtight and electrically conductive. The end of the contact carrier 5 situated within the vacuum chamber is formed as contact member for a further operating contact. The end of the second contact carrier 5 extending out of the vacuum chamber is connected to the other conductor 24 of the alternating current circuit. The first and second contact carriers 4, 5 are in axial alignment with one another.

In the embodiment according to FIG. 1 the two operating contacts 7 and 8 8 are series connected. A supporting bracket 9 is fixed to the casing of the semiconductor diode 11. The free end of the bracket is situated between the contact members of the first and second contact carriers 4 and 5 and is provided with a bore receiving a short third contact carrier 6. This latter is axially movable in the bore in the bracket 9 and its two ends are formed as contact members forming together with the contact members of the first and second contact carriers 4 and 5, the two operating contacts 7 and 8, respectively.

A coiled spring 13 is engaged on the shank of the third contact carrier 6. This spring 13 is supported on the bracket 9 and bears against the contact member of the contact carrier 6 fonning part of the second operating contact 8. A flexible conductor 10 forms an electrical connection with the cathode of the semiconductor diode 11. When the second contact carrier 5 is moved inwardly into the vacuum chamber first the operating contact 8 and then the operating contact 7 which is bridged by the semiconductor diode 11 will be closed. When the second contact carrier 5 is moved outwardly of the vacuum chamber first the operating contact 7 bridged by the semiconductor diode, and then the other operating contact 8 will open. A drive is provided for actuating the second contact carrier 5. For describing the operation, a simple drive is diagrammatically represented in FIG. 1.

The outer end of the second contact carrier 5 is extended by a rod 14 of electrically insulating material. The rod 14 is axially movable with respect to a fixed holding device 17, 18. A spring 16 engaged on the rod 14 between the fixed plate 17 and a washer 30 fixed to the rod urges the rod and the contact carrier 5 in a lower position in which the washer 28 leans against the lower plate 18. In this position of the second contact carrier 5 both operating contacts 7 and 8 are open. The rod 14 is provided with a laterally projecting bolt which, when the second contact carrier is moved inwardly relative to the vacuum chamber and the two pairs of operating contacts 7 and 8 are in closed position, is resting on the end of an armature a of an electromagnet 20, so that the switch is locked with the operating contacts 7, 8 in closed position when the electromagnet 20 is not energized. When the electromagnet is energized, its armature 20a is retracted into the magnet coil against the action of a spring 31 and the bolt 15 is released, so that the contact carrier 5 is pulled outwardly of the vacuum chamber by the action of the spring 16 applying the washer 30 against the fixed plate 18 whereby both operating contacts 7, 8 are opened. The electromagnet 20 can be actuated by the intermediary of a transformer 22 having its primary winding 22!; connected in series with a switch 23 and conductors 26, 27 to the alternating circuit. The secondary winding 22a of the transformer 22, a diode 21 and the coil of the electromagnet 20 are series connected. When the switch 23 is closed the electromagnet is only energized by positive half-waves of the alternating current, i.e., just then when also the semiconductor diode 11 is permeable to current. By suitably selecting the force of the spring 16, it may be obtained that the operating contact 7 bridged by the semiconductor diode 11 opens practically simultaneously with energization of the electromagnet 20. Instead, it is obviously possible to provide a certain delay time upon opening of the operating contact 7, and the diode 21 can be connected with inversed polarity so that it gates a negative half-wave when the switch 23 is closed.

In the embodiment of the vacuum switch according to FIG. 2 the two pairs of operating contacts 7 and 8 are connected in parallel. To the closed end of the bellows 12 are attached the second contact carrier 5 and a supporting arm the free end portion of which receives the third contact carrier 6 and the coiled spring 13 for biasing the contact carrier 6. A contact member 28 is fixed to the casing of the semiconductor diode 11 and is electrically connected by the intermediary of the diode 11 and the closure cap 2 to the first contact carrier 4. The upper end of the third contact carrier 6 is formed as contact member and electrically connected by means of a flexible conductor 10a with the second contact carrier 5. The third contact carrier 6 is movably arranged in the supporting arm 911 so that its upper end together with a contact member 28 fixed to the casing of the semiconductor diode 11 forms an operating contact 8. The coiled spring 13 tends to move the third contact carrier 6 towards the contact member 28, the movement path thereof being limited by an abutment 29. The pair of operating contacts 7, formed by the contact members of the first and second contact carriers 4 and 5 accordingly is bridged by the semiconductor diode l1 and the operating contact 8 connected in series with the diode 11. When the second contact carrier 5 is moved outwardly of the vacuum chamber, first the pair of operating contacts 7 is opened which is bridged by the series connection of the semiconductor diode 11 and operating contacts 8.

The above-described vacuum switch comprises only a single movable contact carrier mounted in a flexible metal bellows. The first and second contact carriers 4, 5 do not absolutely require a vacuumtight lead-through in the closure cap 2 or in the bellows 12. The first contact carrier 4, for example, can be made in two parts. One part carrying the contact member can be fixed to the inside of the closure cap 2, and a second part for connection to the alternating circuit can be fixed to the outside of the cap, so that the cap 2 does not at all require a hose. Also the second contact carrier 5 can be mounted in similar manner when the bellows 12 already is formed with a vacuumtight bottom end. In this case, only the bellows 12 must be sealed in vacuumtight connection to the closure cap 12, and this can be done without any difficulty, since both parts consist of metal. After having mounted the contact carriers to the closure cap 2 and the bellows 12, respectively and the bellows to the closure cap 3, only the two caps must be sealed in vacuumtight connection to the envelope 1, which also does not cause any difficulties.

I claim:

1. A vacuum switch for alternating current interruption comprising a vacuum chamber, two pairs of separable operating contacts disposed in said chamber and connected in an alternating circuit, a semiconductor diode mounted within said vacuum chamber to bridge one of said pairs of operating contacts, drive means for actuating said operating contacts to interrupt the alternating circuit, said drive means being operable to open said pair of operating contacts bridged by said semiconductor diode prior to opening of the other pair of operating contact, and control means associated with said drive means to admit actuation of said operating contacts only when the alternating voltage applied to said semiconductor diode is poled for gating.

2. A vacuum switch according to claim I and comprising a vacuum chamber formed by a cylindrical envelope of electrically insulating material and by two end closure caps fixed to the envelope in vacuumtight connection, a first contact carrier fixed to one of said closure caps, said semiconductor diode being mounted on the inside of said one closure cap and one of the terminals of the semiconductor diode being electrically connected with said first contact carrier, a resilient bellows fixed to the other of said closure caps in vacuumtight connection, a second contact carrier fixed to said bellows in vacuumtight connection, said drive means being operable to move said second contact carrier towards and away from, said first contact carrier, a third, movable contact carrier electrically connected with the other terminal of said semiconductor diode, said third contact carrier being mounted intermediate of and in axial alignment with said first and second contact carriers and defining with said first and second contact carriers, respectively, said two pairs of operating contacts, and spring means biasing said third contact carrier whereby when moving said second contact carrier outwardly of said envelope first the pair of operating contacts bridged by the semiconductor diode and then the other pair of operating contacts separate.

3. A vacuum switch according to claim 1 and comprising a vacuum chamber fonned by a cylindrical envelope of electrically insulating material and by two metallic end closure .caps fixed to the envelope in vacuumtight connection, a first contact carrier fixed to one of said one closure cap and one of the terminals of the semiconductor diode being electrically connected with said first contact carrier, a contact member connected to the other terminal of said semiconductor diode, a resilient bellows fixed to the other of said closure caps in vacuumtight connection, a second contact carrier fixed to said bellows in vacuumtight connection, said drive means being operable to move said second contact carrier towards and away from, said first contact carrier, said first and second contact carriers together defining one of said pairs of operating contacts, a third contact carrier movable together with said second contact carrier and electrically connected therewith, said third contact carrier cooperating with said contact member connected to said other terminal of the semiconductor diode to define the other pair of operating contacts, and spring means biasing said third contact carrier whereby when moving said second contact carrier outwardly of said envelope first the pair of operating contacts formed by said first and second contact carriers will separate and then the other pair of operating contacts formed by said third contact carrier and said contact member connected to the semiconductor diode will separate. 

1. A vacuum switch for alternating current interruption comprising a vacuum chamber, two pairs of separable operating contacts disposed in said chamber and connected in an alternating circuit, a semiconductor diode mounted within said vacuum chamber to bridge one of said pairs of operating contacts, drive means for actuating said operating contacts to interrupt the alternating circuit, said drive means being operable to open said pair of operating contacts bridged by said semiconductor diode prior to opening of the other pair of operating contact, and control means associated with said drive means to admit actuation of said operating contacts only when the alternating voltage applied to said semiconductor diode is poled for gating.
 2. A vacuum switch according to claim 1 and comprising a vacuum chamber formed by a cylindrical envelope of electrically insulating material and by two end closure caps fixed to the envelope in vacuumtight connection, a first contact carrier fixed to one of said closure caps, said semiconductor diode being mounted on the inside of said one closure cap and one of the terminals of the semiconductor diode being electrically connected with said first contact carrier, a resilient bellows fixed to the other of said closure caps in vacuumtight connection, a second contact carrier fixed to said bellows in vacuumtight connection, said drive means being operable to move said second contact carrier towards and away from, said first contact carrier, a third, movable contact carrier electrically connected with the other terminal of said semiconductor diode, said third contact carrier being mounted intermediate of and in axial alignment with said first and second contact carriers and defining with said first and second contact carriers, respectively, said two pairs of operating contacts, and spring means biasing said third contact carrier whereby when moving said second contact carrier outwardly of said envelope first the pair of operating contacts bridged by the semiconductor diode and then the other pair of operating contacts separate.
 3. A vacuum switch according to claim 1 and comprising a vacuum chamber formed by a cylindrical envelope of electrically insulating material and by two metallic end closure caps fixed to the envelope in vacuumtight connection, a first contact carrier fixed to one of said one closure cap and one of the terminals of the semiconductor diode being electrically connectEd with said first contact carrier, a contact member connected to the other terminal of said semiconductor diode, a resilient bellows fixed to the other of said closure caps in vacuumtight connection, a second contact carrier fixed to said bellows in vacuumtight connection, said drive means being operable to move said second contact carrier towards and away from, said first contact carrier, said first and second contact carriers together defining one of said pairs of operating contacts, a third contact carrier movable together with said second contact carrier and electrically connected therewith, said third contact carrier cooperating with said contact member connected to said other terminal of the semiconductor diode to define the other pair of operating contacts, and spring means biasing said third contact carrier whereby when moving said second contact carrier outwardly of said envelope first the pair of operating contacts formed by said first and second contact carriers will separate and then the other pair of operating contacts formed by said third contact carrier and said contact member connected to the semiconductor diode will separate. 